The present invention relates generally to techniques for manufacturing integrated circuit (IC) dies and, more particularly, to techniques for separating individual IC dies from multi-die wafers.
Multiple copies of an IC die are fabricated on a semiconductor (e.g., silicon) wafer. Individual dies are separated by mounting the wafer onto a substrate (such as a plastic dicing tape) using a layer of adhesive such as a die attach film (DAF) or film over wire (FOW) material, and then using a saw to cut along saw streets located between the dies. For thin IC dies, such blade dicing can result in backside chipping of the die.
To limit backside chipping, a dice-before-grind (DBG) technique can be employed to separate IC dies. In DBG, the separation occurs during a wafer-thinning step. In particular, a blade or laser beam is applied to the front side of the wafer to partially cut the wafer to a depth below the target thickness of the dies. A supporting “substrate” material such as back-grinding tape then is mounted on the front side of the wafer, and mechanical grinding is performed on the wafer backside to thin the wafer to the target thickness, thereby separating the individual dies. Dicing tape, DAF, or FOW is then applied to the backside of the wafer for the next process step, such as die pick-up.
Another alternative to blade dicing is stealth dicing (SD) in which defect regions are introduced into the wafer by scanning a laser beam along intended cut lines, and then the underlying substrate is expanded to induce fractures in the wafer along the cut lines, thereby separating the individual dies.
In both DBG and SD, following the separation of the wafer into individual dies, the separated dies are still mounted on the substrate by the adhesive layer. So that pick-and-place machinery can safely remove individual dies from the substrate, the adhesive layer must be separated such that each die is supported on the substrate by a corresponding portion of adhesive material that is separated from the portions of adhesive material corresponding to adjacent dies. A laser can be used to remove the adhesive material from between adjacent dies to form these separate adhesive portions, but any misalignment of the laser beam can result in damage to the dies. Accordingly, it would be advantageous to have a reliable and cost-effective method of separating dies formed on a wafer, and removing the dies from a carrier substrate, that avoids die backside chipping.